From memory because I HAD but no longer do have a 750.
Brutal perhaps, but make the sequence begin and switch off....
A bit like trying to judge when the windscreen wipers are vertical in an old car about to suffer an unsympathetic car wash.
There may be other trouble in the background and if the black pathway is dry, it may be worth being very patient -
A couple of head cleaning procedures and then leave overnight to let ink diffuse along the pathways and for all micro bubbles to disperse.